Unidirectional Linecards for Higher Multi-Stage Clos Throughput
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Solution Overview
Problem
Existing Clos topologies do not fully exploit the radix of switches in the lower stage, limiting the throughput of non-blocking networks.
Innovation Solution
Replace conventional switches in the lower stage with linecards composed of two unidirectional switch chips, one forwarding information from the access stage to the upper stage and the other from the upper stage to the access stage, ensuring separate connections for incoming and outgoing traffic.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional switches are used in the lower stage, then the network structure is simple, but the non-blocking throughput is limited and the switch radix is not fully exploited
Solution Approach 1:
The patent segments each lower stage switch into two separate unidirectional switching components: one dedicated to upward traffic (access to upper stage) and one dedicated to downward traffic (upper stage to access). This segmentation allows each component to operate at full capacity without contention, effectively doubling the non-blocking throughput while maintaining a relatively simple overall network structure
Solution Approach 2:
The patent combines two unidirectional switching components within each line card to form a complete bidirectional switching function. By merging these specialized components, the system achieves full switch radix utilization while avoiding the complexity of reconfigurable switches, as each component has a fixed, dedicated function
2Productivity
If switches in the lower stage forward to all ports, then connectivity is maximized, but the switch radix is not fully exploited and throughput is limited
Solution Approach 1:
The patent extracts the bidirectional forwarding function from a single switch and separates it into two dedicated unidirectional forwarding components. Each component handles only one direction of traffic, allowing both to operate at maximum throughput without the overhead of managing all-to-all port connectivity in a single switching fabric
Solution Approach 2:
Instead of using a single switch that attempts to handle all forwarding decisions, the patent inverts the approach by using two specialized unidirectional switches, each optimized for a specific traffic direction. This inversion allows each component to be simpler and more efficient, achieving higher overall throughput
Data Source
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AI summary
A novel multi-stage folded Clos network and a linecard for use in a network is disclosed. The Clos network can consist of three stages, an access stage, a lower stage, and an upper stage. The access stage and the upper stage can include a plurality of switches or conventional access points. The lower stage can include a plurality of linecards. Each linecard can be made of two switch chips, each of which are connected to the ports of the linecard, and contain the same number of ports. Each switch chip can forward information in only one direction and one is used to send direction from the access stage to the upper stage, and the other from the upper stage to the access stage. The lower stage can consist of a number of sub-stages, each sub-stage can be entirely of either conventional switches or linecards. Accordingly, compared to a conventional Clos network, the provided network can increase the throughput by any power of 2 by replacing the conventional switches used in the lower stage or sub-stages with linecards.